1. Field of the Invention
This invention relates generally to voltage regulators, and more specifically to voltage regulators in an integrated circuit.
2. Related Art
A low-dropout regulator is implemented in circuit applications to provide a regulated power supply. A low-dropout regulator is a DC linear voltage regulator that has a very small input-to-output differential voltage.
FIG. 1 is a known circuit 100 that illustrates the manner in which a known low-dropout voltage regulator 108 is used. The circuit 100 includes an integrated circuit (IC) 101 within an IC package 102. The known regulator 108 is one of a plurality of circuits on the IC 101. The IC package 102 has a plurality of pins 103 for connecting the IC 101 to circuits external to the IC package 102. A battery 120 supplies power to the regulator 108 via a power pin 122. An output 130 from the regulator 108 is also coupled to power-out pin 132 via a metal run 124 on the IC, and a wire bond 126 between a bond pad 128 at an end of the metal run on the IC and an internal portion 131 of the power-out pin 132. An external capacitor 140 is coupled between the power-out pin 132 and ground. The known circuit 100 includes an external metal run 134 between an external portion 136 of the power-out pin 132 and a load pin 142. The IC 101 includes a load circuit 110 coupled to the load pin 142. The regulator 108 provides a regulated voltage to the load circuit 110.
One of the important aspects of any voltage regulator is load regulation. Unless compensated for, the output voltage of a voltage regulator decreases as the output current increases. The output voltage from a voltage regulator varies as a function of the output, or load, current because of a presence of a plurality of resistances in the coupling between the regulator and its load.
There is a voltage drop between the output 130 of the known regulator 108 and node 138 that is caused by a total resistance between the output 130 of the regulator 108 and node 138. The total resistance includes the resistance due to the metal run 124 on the IC 101 between the output 130 of the regulator 108 and a bond pad 128 at an end of the metal run, the resistance due to the connection with the wire bond 126 at the bond pad, the resistance of the wire bond, and the resistance of the power-out pin 132 and connections thereat. The known regulator 108 requires that the voltage drop at node 138 due to the total resistance be compensated for. A typical known regulator 108 determines the total resistance by measuring the voltage at node 138. Then, the typical regulator 108 places the amount of the voltage drop (between the output 130 and node 138) into a feedback loop (not shown) within the known regulator so that the desired regulated voltage appears at node 138. The known regulator 108 senses the voltage at node 138 via a sense pin 182 on the IC package 102. Therefore, the known regulator 108 disadvantageously requires the sense pin 182 in addition to the power-out pin 132.